I think they did a lot of work to that bike to be able to ride it like that.
I had the new Bonneville and no way I would dirt ride it on anything else but hard smooth dirt roads, which is mostly what is in the video.
I have had a number of dual sports and old bikes over the years, and yes, many of the older bikes did quite well in the dirt, even a stock cb350 was fun and quite tough.
The weight of the TU is good, the motor is great for the dirt, but everything else sucks.
The back shocks I can live with, but the forks just won't do.
You only have 3 inches of travel, they waste over an inch in the full compression bump stop which is really just a hydrolock setup where the damping goes WAY up and stops the forks from bottoming.
If you drain the oil out, you could get over 4 inches...
I have looked into making it softer so you could use some of the travel, but have not tried it yet.
The old bikes had little headlights and wide bars that prevented damage, they had the controls tucked in better, and with old Triumphs, had rigid mounted pegs that did not fold. I crashed my old Daytona way too many times and never broke anything (on the bike).
You would at least have to do something with the TU foot pegs, just a little air and they bend down.
One minor fall and you would likely rip off the brake pedal or shifter, break the levers and/or their mounts, bust the $400.00 headlight, dent the wide $600.00 gas tank, and bust a turn signal or two.
In rougher stuff, the 18 inch front wheel and the 3 inches of fork travel make for a very nasty ride.
Its just not worth it to do all that would be needed to make things good, and it would ruin the great street performance of the TU.
I am looking for something vintage that would be fun as a dual sport.
I have a list of bikes that might do better then the TU, all are old and some are very old.
Any old 350 to 500cc single or twin that is not super heavy is in the running.
At the top of the list is a late model sl350 I think.
If I was set up to weld, it might open up lots of other bikes, gn400, cb350, s40 savage, sr500, Honda 500 Ascot, sx650, even an old solid frame chain drive 883 sportster.